Cosmic inflation provides a compelling mechanism for the generation of primordial fluctuations—as the universe expands and flattens, quantum mechanical vacuum fluctuations are stretched to cosmological distances. During the past decades and more recently from the Planck mission [1]}, measurements of the CMB fluctuations have shown consistency with the predictions of slow-roll models of inflation: superhorizon primordial fluctuations are nearly scale-invariant, adiabatic and nearly Gaussian.
While the single field slow-roll model predicts a small amount of non-Gaussianity [2]}, [3]}, coming from gravitationally mediated self-interactions of the inflaton, other models of inflation predict stronger signals.
Different physical processes, mediated by particles with masses of order the Hubble scale during inflation, give rise to distinctive signatures in the non-Gaussian signal. The precision calculation of such signatures is a rich subject, much akin to the area of scattering amplitudes in particle physics. In certain kinematical configurations, such as squeezed and collapsed limits, the shape of non-Gaussianity reveals information about the mass and the spin of particles mediating the interactions among the curvature fluctuations [4]}, [5]}, [6]}, [7]}, [8]}. Generally, the \(N\) -point correlation functions of the primordial curvature fluctuations are given by
\(\langle \zeta _{k_1}\zeta _{k_2}\cdots \zeta _{k_N}\rangle =\delta ^{(3)}(k_{12\dots N}) F_\zeta (k_1,\dots ,k_N)\) 
